Method for identifying a degree of soiling of a cooking appliance interior

ABSTRACT

A method for identifying a degree of soiling of an interior of a cooking appliance, in particular of the cooking chamber, during at least one of a cleaning operation and a cooking operation and a method for cleaning such a cooking appliance interior include determining at least one parameter of a liquid and a degree of soiling.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of foreign priority to DE 10 2017 111 249.9 and DE 10 2017 111 246.4, both filed on 23 May 2017, each of which is herein incorporated by reference in its entirety for all purposes.

BACKGROUND 1. Field of the Invention

The following description relates to a method for identifying the degree of soiling of an interior of a cooking appliance, in particular of the cooking chamber, during a cleaning operation and/or a cooking operation and relates to a method for cleaning a cooking appliance interior as a function of a degree of soiling.

2. Related Art

Cooking foods results in soiling in the cooking chamber of the cooking appliance used, for example on the walls, ceiling or floor. Different types of soiling arise here, for example caused by proteins, carbohydrates, carbonates, sugars and/or fats, with different degrees of soiling, specifically depending on the foodstuffs to be cooked and the duration of use between cleaning phases. Due to the different soiling, cleaning of the cooking appliance requires a cleaning method which is specifically adapted to the soiling. Modern cooking appliances permit the selection of various cleaning methods, but during the actual cleaning do not permit any change to the cleaning parameters, such as for example temperature and quantity of cleaning agent, in particular in response to the current degree of soiling during the cleaning phase. This is, however, desirable in order to extend the service life of the appliance, save costs and avoid any needless environmental impact, in that smaller quantities of cleaning agents and less energy are required during the actual cleaning operation.

DE 10 2007 005 501 A1, for example, describes a method for cleaning a food processing appliance, in which the degree of soiling over a period between two cleaning cycles is evaluated and the cleaning program adapted accordingly. Adaptation of the cleaning method during cleaning is not provided.

DE 10 2007 005 503 describes a method for cleaning at least one surface within at least one interior and/or container of a food processing appliance by introducing at least one cleaning fluid into the interior and/or container as well as an abrasively acting granular material which, depending on the temperature, is at least partially dissolved in the cleaning fluid.

DE 20 2006 003 365 U1 describes a cooking appliance which inter alia has sensors which measure the physical parameters of a liquid.

WO 03/073002 A1 describes a method for cleaning an interior of a cooking appliance, in which the interior is cleaned with a cleaning fluid during at least one cleaning cycle and rinsed with water at the end of the cleaning cycle. A tab is here introduced into the interior for example via a hatch. The hatch can be opened or closed as a function of a time controller and/or the degree of soiling, in particular determined via at least one turbidity sensor, without any details in this connection being described.

SUMMARY

In an aspect, a method for identifying the degree of soiling during cleaning and/or cooking of a cooking appliance interior which verifies the particular current degree of soiling in order to be able in particular to adapt a currently running cleaning method or determine future cleaning methods is described. In addition, a method is provided for cleaning a cooking appliance interior which permits adaptation of a cleaning operation to the particular degree of soiling during the cleaning operation, in particular by determining the degree of soiling of a washing liquor located in the cooking appliance interior at any desired point in time of the cleaning operation. The invention thus provides a flexible, inexpensive and environmentally responsible method which ensures clean interiors in cooking appliances in the most efficient manner.

In an aspect, a method for identifying the degree of soiling of an interior of a cooking appliance, in particular of the cooking chamber, during a cleaning operation and/or a cooking operation includes determining at least one parameter of a liquid over time and determining the degree of soiling of the interior from the change in the at least one parameter and wherein the at least one parameter is a physical variable which is determined via at least one sensor.

It may be provided that at least one first parameter of the liquid is determined at a first point in time of the cleaning or cooking operation and at least one second parameter of the liquid is determined at a second point in time of the cleaning or cooking operation; and the degree of soiling is determined from the change in and/or difference between the first and second parameters and comparing the change in and/or difference between the first and second parameters with at least one predetermined or predeterminable limit value.

Preferably, in order to determine the degree of soiling at a plurality of points in time, the at least one parameter is detected, and/or the progression of the at least one parameter over time is detected, and/or at least one maximum and/or at least one minimum of the progression of the at least one parameter over time is detected, and/or the gradient and/or curvature of the progression of the at least one parameter over time is detected and/or a regression analysis of the parameters is carried out.

It is furthermore proposed that the time interval between two successive measurements is lengthened or shortened, in particular via the open- or closed-loop control device, as a function of the detected parameters, the detected progression of the parameters, the detected maximum of the progression of the parameters, the detected minimum of the progression of the parameters, the detected gradient and/or curvature of the progression of the parameters and/or the regression analysis.

It may also be provided that the degree of soiling and/or at least one, in particular previously carried out program, selected from a plurality of cleaning programs and/or cooking programs, is determined, in particular via the open- or closed-loop control device, as a function of the detected parameters, the detected progression of the parameters, the detected maximum of the progression of the parameters, the detected minimum of the progression of the parameters, the detected gradient and/or curvature of the progression of the parameters and/or the regression analysis.

The identified or determined degree of soiling may be displayed at least temporarily, preferably automatically or on request.

A further embodiment provides a method for cleaning a cooking appliance interior which comprises the following steps after the start of a cleaning operation having at least one cleaning phase: a) introducing a washing liquor into the cooking appliance interior and starting the at least one cleaning phase using one or more cleaning parameters; b) determining at least one first parameter TS₁ of the washing liquor at a first point in time t₁ of the cleaning operation and determining at least one second parameter TS₂ of the washing liquor at a second point in time t₂ of the cleaning operation; and c) determining the degree of cleaning of the cooking appliance interior from the change in the parameters; wherein, depending on the change in the parameters, steps a) to c) are repeated and/or at least one of the cleaning parameters is adapted or the at least one cleaning phase is terminated.

In order to determine the degree of cleaning at a plurality of points in time, the at least one parameter may be detected, and/or the progression of the at least one parameter over time may be detected, and/or at least one maximum and/or at least one minimum of the progression of the at least one parameter over time may be detected, and/or the gradient and/or curvature of the progression of the at least one parameter over time may be detected and/or a regression analysis of the parameters may be carried out.

It may furthermore be provided that the degree of cleaning of the cooking appliance interior is determined from the change in and/or difference between the first parameter relative to the second parameter, ΔTS₁=TS₂−TS₁, and by comparing the change in and/or difference between the parameters with at least one known limit value TS_(limit).

Initial cleaning parameters may be determined by determining at least one parameter TS₀ at a point in time t₀ and/or by manual selection of a cleaning program.

It is proposed that at least one of the parameters of the cleaning operation is paused prior to determination.

It may additionally be provided that the first point in time t₁ is selected during the at least one cleaning phase and the second point in time t₂ after the at least one cleaning phase, wherein the cleaning operation is preferably terminated when the at least one limit value is reached.

Furthermore, as a function of the identified or determined degree of cleaning, at least one cleaning parameter, at least one limit value and/or at least one time interval between the determination of two parameters may be determined, stored and/or displayed for at least one subsequent cleaning phase of the cleaning operation and/or a future cleaning operation.

Likewise, as a function of the identified or determined degree of cleaning, at least one cleaning parameter of at least one previous cleaning phase of the cleaning operation may be determined, stored and/or displayed.

Also, as a function of the identified or determined degree of cleaning, at least one characteristic variable of at least one previous cooking operation may be determined, stored and/or displayed and/or, as a function of the identified or determined degree of cleaning, a user behavior may be determined, stored and/or displayed.

The at least one determined or adapted cleaning parameter may be selected from the duration of the at least one cleaning phase, the temperature during the at least one cleaning phase, the speed of circulation of the cleaning agent, the acceleration of circulation of the cleaning agent, the chemistry of the cleaning agent, the quantity of cleaning agent and/or the quantity of washing medium, in particular water.

The at least one cleaning phase may be selected from a cleaning product phase, a rinse aid phase and/or a descaler phase, and/or the chemistry of the cleaning agent can be selected from a cleaning product, a rinse aid and/or a descaler.

The minimum of the time progression of parameters for turbidity may here be detected or determined and, on the basis of the parameter at the minimum, the degree of soiling may be determined, wherein the parameter at the minimum is smaller at a greater degree of soiling.

It may additionally be provided that, as a function of the identified or determined degree of soiling, an ongoing cleaning operation is adapted and/or a suggestion for and/or a modification to a future cleaning program is determined and/or at least one characteristic variable of a previous and/or the current cooking operation is determined and/or a user behavior is determined.

The liquid selected may be a washing liquor during a cleaning operation or a water reserve upstream from an outlet of the cooking appliance during a cooking operation.

It may here be provided that the cleaning operation is paused during a cleaning operation prior to determination of at least one of the parameters. It may in turn here be provided that the duration of the pause in the cleaning operation and/or the timing of the pause in the cleaning operation is determined, in particular via the open- or closed-loop control device, as a function of the detected parameters, the detected progression of the parameters, the detected maximum of the progression of the parameters, the detected minimum of the progression of the parameters, the detected gradient and/or curvature of the progression of the parameters.

At least one parameter of a liquid, namely preferably a washing liquor located in the cooking appliance interior or a water reserve located downstream of the cooking chamber, may be determined over time in order to allow the degree of soiling of the cooking appliance interior to be determined from the change in the at least one parameter, wherein the at least one parameter is a physical variable which is determined via at least one sensor. The physical variable is preferably the turbidity.

The at least one sensor may be installed in the cleaning path of the washing liquor or liquid, the pump sump, the cooking chamber, the cleaning product box and/or downstream (in a pipe) of the cooking chamber and/or an open- or closed-loop control device carries out the measurement and/or the evaluation of the measured values obtained, wherein the open- or closed-loop control device preferably includes the at least one sensor.

The at least one parameter may be a physical variable which is selected from the turbidity, pH, conductivity, viscosity, color, refractive index, fluorescence, adsorption, emission and/or density of the washing liquor, and/or for the at least one sensor to be selected from an optical sensor, a turbidity sensor, a pH sensor, a conductivity sensor, a viscosity sensor, a color sensor, a sensor for measuring refractive index, a fluorescence sensor, a sensor for measuring adsorption and/or emission and/or a density sensor.

A washing liquor means a mixture of one or more washing media and one or more cleaning agents which are introduced in particular into the cooking chamber of the cooking appliance via corresponding feed line(s) or devices provided for this purpose. A suitable washing medium is water. The one or more cleaning agents are for example cleaning products, rinse aids and/or descalers. Cleaning agents may be solid or liquid, wherein they are in particular used in the form of tabs, for example as single-phase tabs (which comprise just one cleaning agent or one auxiliary) or multi-phase tabs (which comprise various cleaning agents and auxiliaries, usually in a plurality of layers/zones). The one or more cleaning agents may be added by manual or automatic dispensing, for example by the initially used cleaning program, via corresponding dispensers. The one or more cleaning agents may also be dispensed, preferably automatically, only once the first parameter has been determined at the beginning of the cleaning method. For example, the one or more cleaning agents may be dispensed, preferably automatically, only once a first parameter T₀ and a resultant degree of soiling have been determined at a point in time t₀ at the beginning of the cleaning method. The cleaning agents may simultaneously be present in the washing liquor in any combination or are used in succession in different cleaning phases. For example, the method may first of all be carried out with a washing liquor consisting of washing medium and cleaning fluid, cleaning powder or cleaning tabs. Thereafter, a rinsing phase may then for example be carried out.

A water reserve may include a liquid substantially consisting of water in a condenser and/or a cleaning tank connected thereto, which may also be denoted pump sump, since the condenser and/or the cleaning tank is normally connectable with the interposition of at least one pump to an outlet of the cooking appliance and/or to a return line to the cooking chamber.

The cleaning parameters are for example provided by selecting a specific cleaning program. The cleaning program may be suggested by the cooking appliance or may be selected manually. In one embodiment, the cleaning parameters may also be automatically selected and applied depending on the degree of soiling of the cooking appliance interior only once the first parameter of the liquid has been determined. In another embodiment, the cleaning parameters may also be automatically selected and applied depending on the degree of soiling of the cooking appliance interior only once a first parameter TS₀ of the washing liquor has been determined at a point in time t₀ at the beginning of the cleaning method. It is also possible to change cleaning parameters manually. Cleaning parameters are for example temperature, duration of a cleaning phase, chemistry of the cleaning agent used or quantity of cleaning agent used, without being limited thereto. A cleaning program may additionally comprise a plurality of different cleaning phases which are in each case determined by cleaning parameters.

The at least one parameter of the washing liquor may be determined over time during a cleaning operation after the start thereof and introduction of the washing liquor into the cooking appliance interior, in particular into the cooking chamber of the cooking appliance. The change in the parameter provides information about the current degree of soiling of the washing liquor.

In the case of measurement of soiling during a cooking operation, the water reserve is soiled during said operation for example with juice released from a foodstuff being cooked, such that the soiling of the cooking chamber is determinable via the detection of the at least one parameter of the water reserve over time. The change in the parameter here again provides information about the current degree of soiling.

In one embodiment, the difference in the parameters obtained results in a measured variable, on the basis of which a conclusion may be drawn about the degree of soiling for example of the washing liquor during a cleaning operation and thus the degree of cleaning of the cooking appliance interior. At least one first parameter of the washing liquor may here be determined at a first point in time t₁ of the cleaning operation and at least one second parameter of the washing liquor at a second point in time t₂ of the cleaning operation, such that the degree of soiling may be determined from the change in and/or difference between the parameters at points in time t₁ and t₂ and comparing the change in and/or difference between the parameters with a known limit value. In a further embodiment, a plurality of parameters provides insight into the degree of soiling.

The respective parameters may be determined by at least one sensor. Such a sensor may be arranged at any suitable position in the cooking chamber, i.e. the cooking appliance interior or downstream of the cooking appliance interior, such that the parameter may be optimally determined with the result that the parameter is ascertained as accurately as possible. The at least one sensor may preferably be installed in the cleaning path of the washing liquor, in a control box, the pump sump, the cooking chamber, a cleaning tank, a condenser and/or a pipe of the cooking appliance. The method may use more than one sensor, for example two, three or four or more sensors. Identical sensors may here be arranged at different positions of the cooking appliance. In a further embodiment, a plurality of different sensors may be arranged in the cooking appliance so that different parameters may be ascertained, which may result in a further improvement in measuring accuracy and thus in determination of the degree of soiling.

The at least one sensor may be a sensor for measuring the turbidity, pH, electrical conductivity, viscosity, color, refractive index, fluorescence, adsorption, emission and/or density of the washing liquor. Further types of sensors which may be used to determine the degree of soiling or degree of cleanliness are possible but a turbidity sensor is preferred. The above-stated sensors are known to a person skilled in the art and may, as described above, be used individually or also in combination. The respective parameter of the liquid determined by the sensor(s) provides information about the degree of soiling of the cooking appliance.

The at least one parameter is a physical variable selected from the turbidity, pH, electrical conductivity, viscosity, color, refractive index, fluorescence, adsorption, emission and/or density of the washing liquor. Further physical variables which are suitable for determining the degree of soiling are possible.

An open- or closed-loop control device may carry out or initializes the respective measurements, for example at points in time t₁ and t_(2.) The first measurement is for example carried out during a cleaning operation at a predetermined point in time, for example at a predetermined point in time t₁, advantageously shortly after the start of a first cleaning phase in order to obtain a first parameter, for example a first parameter TS₁ . In one embodiment, the first measurement is carried out directly after introduction of the washing liquor into the cooking appliance interior. The time interval or time gap between the individual measurements, for example between points in time t₁ and t₂, is preset, but can also be manually modified in order to ensure the degree of soiling is determined as accurately as possible. The time interval between two measurements is, for example, 45 seconds, 60 seconds, 90 seconds, 2 minutes, 5 minutes or any other suitable time interval. This time interval is generally sufficient to draw a conclusion about the degree of soiling from the values obtained, for example a first parameter TS₁ and a second parameter TS_(2.) On the basis of the parameters obtained, the open- or closed-loop control device can, as required, lengthen or shorten the time interval between the measurements. One embodiment provides acquiring a plurality of measured values simultaneously or within a very short interval and calculating an averaged parameter from the ascertained measured values. In this manner, it is possible to achieve an increase in measuring accuracy and to take account of the fact that cleaning does not proceed entirely linearly. In one embodiment, a parameter TS₀ is determined at a point in time t₀ right at the beginning of the cleaning operation and, as a consequence of this value, the first, i.e. the initial, cleaning parameters are determined.

On the basis of the parameters obtained, for example at points in time t₁ and t_(2,) it is possible to draw a conclusion about the current degree of soiling of the cooking chamber, about the progression in the state of soiling, about the current state of cleaning or about the progression in the state of cleaning. For example, the difference between two values may be compared with a known or defined limit value. For example, should the value obtained be above the limit value, this may mean that a significant change in the degree of soiling is still taking place and the cleaning method must be continued. In another embodiment, should the limit value not have been reached over the course of a cleaning phase, this means that a significant change in the degree of cleaning is still taking place, such that a further cleaning phase is necessary. Depending on the measured parameter, not achieving the limit value may here mean that the limit value has been exceeded or fallen below. In one embodiment, the parameter at the point in time t₂ itself provides information about the degree of cleaning.

If the measurement reveals during a cleaning operation that cleaning has to be continued, a subsequent or further cleaning phase may be carried out with the same parameters as the first or preceding cleaning phase. In another embodiment, however, the parameters of the cleaning operation or cycle are changed in response to the parameters obtained, such that for example the temperature, the additionally supplied quantity of cleaning agent or the duration of the subsequent cleaning phase is adapted to the progression in the parameters.

After a further time interval, a subsequent parameter may be or is determined, wherein the time interval may be identical to the first time interval between the determination of the parameters, as described above. By maintaining the time interval between the individual measurements, the degree of soiling or achieved degree of cleaning can be determined continuously and thus consistently. In one embodiment, the time interval for determining the subsequent parameter may be different from the preceding time interval, for example in response to the hitherto achieved degree of cleaning or degree of soiling still remaining.

In one embodiment, the parameters obtained, i.e. a plurality of parameters obtained over time, may be combined by the open- or closed-loop control device to yield a measurement curve, such that the progression thereof may be evaluated by suitable mathematical algorithms. For example, a statement about the degree of soiling or degree of cleaning can be made on the basis of the gradient of the curve, a derivative function, determination of maxima and/or minima or by specific filtering of the measured values. In one embodiment, a regression analysis of the parameters can be carried out. Irrespective of the nature of the calculation of the degree of soiling or degree of cleaning, further cleaning of the cooking appliance can be adapted in line with the result or the cleaning operation terminated, for example when the defined limit value or another measured value, as described above, is reached. As soon as the cleaning operation has been terminated, a rinsing phase, which may be carried out using the method, may follow.

The respective above-described measurement during a cleaning operation may also be carried out only once the pump has been stationary for a predetermined period, i.e. the cleaning operation has come to rest, such that the washing liquor comes to rest and the measurement(s) are not impaired by possible air bubbles or foam or other disruptive factors.

The present method also makes it possible to verify whether preceding cleaning phases have proceeded correctly. For example, by measuring a parameter during the rinsing phase it can be verified whether a cleaning agent has previously been supplied to the cooking appliance or the quantity of cleaning agent was sufficient. Depending on the measured parameter, the cleaning curve declines more slowly, for example, and remains at a low level if no cleaning agent has been added. Conclusions regarding preceding cleaning phases may thus be drawn from the respective parameters for a cleaning phase.

The present method thus makes it possible to determine the current degree of soiling of the cooking appliance during a cleaning operation by determining a physical variable of the washing liquor. This determination in turn permits automatic adaptation and control of cleaning temperature, duration of cleaning, the quantity of cleaning medium used and/or the chemistry and/or quantity of cleaning agent used. A further advantage may include that a plurality of different cleaning programs is not required, but instead the cooking appliance “autonomously” cleans itself optimally by adapting the cleaning parameters. Accordingly, the cleaning method can, for example, automatically determine the cleaning parameters on the basis of an initially determined parameter TS₀.

If, for example, a cleaning operation is started with an environmentally friendly “eco” program, the degree of soiling is determined during the cleaning operation and, as a consequence, if a corresponding degree of soiling is present, additional cleaning agent can for example be supplied or higher cleaning temperatures used. Ultimately, the user is not required to select a suitable cleaning program, since the program can adapt itself to the required cleaning conditions.

In another aspect, a cooking appliance includes an interior and at least one sensor in the interior and/or downstream of the interior, in particular in a cleaning path, for carrying out the method.

Preferably, the cooking appliance is self-learning, thus it in particular uses the respectively ascertained degree of soiling to derive teaching for future operations and also for those under way.

In the case in which a degree of soiling is to be detected during a cooking operation, it is particularly preferred to arrange the sensor in a pump sump which forms a water reserve between the cooking chamber and the outlet of the cooking appliance. Locating the sensor in a condenser and/or cleaning tank arranged between the cooking chamber and the outlet is particularly advantageous for this purpose. In particular in the case of a turbidity sensor being used, it is preferred for the turbidity sensor to be arranged during acquisition of the pump sump parameters in the juices which flow out from the foodstuff during cooking thereof. The water level in the pump sump must therefore be controlled in such a manner that this is ensured.

In other words, a cooking appliance for detecting a degree of soiling during a cooking operation is distinguished in that the sensor is arranged downstream of the cooking chamber with the liquid to be evaluated flowing therearound.

Further, the cooking chamber may be connected, in particular with interposition of a strainer, to a condenser and/or a cleaning tank, and for the sensor to be arranged in the condenser and/or cleaning tank.

The condenser and/or cleaning tank may be connected to an at least temporarily closable outlet and/or to an at least temporarily closable return line to the cooking chamber.

It may here in turn be provided for the outlet to be temporarily closable via a pump or a valve, and/or the return line to be connected to a pump and/or a valve.

It is here preferred for the sensor to be arranged in the water reserve provided by a sump of the pump of the outlet and/or of the pump of the return line.

The sensor may be arranged in the water reserve between the cooking chamber and the outlet from the cooking appliance. The water level of the water reserve is preferably adjustable, in particular via an open- or closed-loop control device in operative connection with the pump of the outlet, the pump, the return line and/or a shut-off device.

A smart cleaning method for a cooking appliance may be provided, in which resources are optimally utilized and thus costs are saved and environmental impact is reduced while satisfactory cleaning performance is simultaneously achieved. This is achieved on the basis of the recognition that different parameters provide an indication about the degree of soiling of an interior, i.e. the severity of the cleaning task.

Further features and advantages of the invention are described by the following description which explains exemplary embodiments of a method according to the invention with reference to schematic diagrams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a parameter progression, in the form of a turbidity change profile (stated in [V]) of a washing liquor in a cooking chamber of a cooking appliance over time;

FIG. 2 illustrates the proportion and size of particles in a washing liquor over the course of the cleaning phase;

FIG. 3 illustrates a parameter progression over a complete cleaning method, including rinsing phase and drying operation;

FIG. 4 illustrates parameter progressions for light, moderate and severe soiling and cleaning with and without the addition of cleaning agent; and

FIG. 5 illustrates a partially sectional view through a cooking appliance;

FIG. 6 illustrates a parameter progression in the form of a turbidity change profile of a washing liquor in a cooking chamber of a cooking appliance;

FIG. 7 illustrates a portion of an automated cleaning method;

FIG. 8 illustrates a complete cleaning method without a subsequent rinsing phase;

FIG. 9 illustrates parameter progressions for cleaning methods without use of cleaning agents.

DETAILED DESCRIPTION

The method is described by way of example on the basis of the determination of turbidity values of the washing liquor, wherein the method can be carried out in a similar manner for any other of the above-stated parameters or any combination of parameters. When a turbidity sensor is used, a low parameter for example means high turbidity, since voltage values are detected which are lower, the smaller the quantity of light is that passes through the washing liquor and impinges on a sensor due to the turbidity of the washing liquor.

After the start of a cleaning program and introduction of washing liquor into the cooking chamber of a cooking appliance, a cleaning phase is started which uses the cleaning parameters, such as for example a defined temperature with a predetermined cleaning agent. FIG. 1 shows by way of example a possible parameter progression over time (cleaning progress). At the beginning of cleaning, the turbidity in the washing liquor may for example increase sharply. Thereafter, turbidity does not increase any further, but instead declines. This is for example because, without being limited thereto, a very large number of particles which are detached from the cooking chamber wall are present in the washing liquor at the beginning of cleaning. These numerous particles cause severe diffraction of the light. These first turbidity values provide direct information about how severely the cooking appliance interior is soiled. In the case of slight soiling, the decline in the curve is correspondingly low, while the decline is greater in the case of severe soiling and thus severe turbidity of the washing liquor. Turbidity then falls during cleaning, as the appliance thus becomes cleaner, since more soil particles dissolve in the washing liquor than new ones are detached in the cooking chamber. The turbidity curve rises as a consequence.

The proportion of particles in the washing liquor and thus the degree of turbidity can be taken from FIG. 2, wherein it is apparent that the particles become ever smaller over the course of time and ultimately completely dissolve, such that turbidity declines or, ideally, disappears.

As is apparent from progression 1 in FIG. 1, in a cooking appliance with severe soiling, the curve declines rapidly right at the beginning of measurement, specifically to a minimum M₁, while in the case of severe soiling the further progression can be observed to continue virtually horizontal with a high level of turbidity. In the case of slight soiling, the curve likewise initially declines, as is apparent from progression 2 in FIG. 1 with the minimum M₂, but not as low as in a cooking appliance with severe soiling, since less turbidity of the washing liquor is present. In other words, M₂ is greater than M_(i). In progression 2, after the minimum M₂, a distinct upward rise is apparent, since turbidity declines relatively rapidly as a consequence of the reducing degree of soiling. In the case of very slight soiling, as indicated with progression 3 in FIG. 1, after a first decline of the curve to a minimum M₃, the progression becomes virtually horizontal with a relatively low level of turbidity. Minimum M₃ is higher than minimum M₂.

The degree of soiling can thus in particular be inferred from the minimum of the turbidity value progression. The lower the detected voltage value at the minimum during the turbidity value progression, the greater is the degree of soiling.

FIG. 3 shows the curve progression for further cleaning tests. It is apparent that at the beginning of a cleaning phase (2) the measured value for turbidity, i.e. voltage, declines sharply, which correlates with severe soiling or for example indicates that the appliance has not previously been cleaned or not adequately cleaned. Over the course of the cleaning operation, the measured value rises due to the reduction in the degree of soiling. At the end of the cleaning phase (2), the determined parameter is below a defined limit value and the cleaning phase (2) is terminated such that a new phase (3) can follow. Phase (3) is a rinsing phase with a peak which is characteristic for this phase and which indicates that a rinse aid has been added. The final phase (4) shown is a drying operation.

FIG. 4 shows typical parameter curve progressions which are indicative of slight, moderate or severe soiling. The decline differs in extent depending on the soiling the lower the decline extends, the greater the soiling. The curve progression is likewise dependent on the “tenacity” of the soiling and/or the quantity of soiling and is characteristic of the respective state. The curve progressions of FIG. 4 also show that no rinsing has been carried out, since there is no peak which is characteristic thereof

FIG. 5 shows a cooking appliance 1 with its cooking chamber 10 which is connected to a condenser 20 and cleaning tank 24. The cooking chamber 10 is here connected to the condenser 20 via a drain 12, in which a strainer 14 for separating coarse soiling is arranged. The strainer 14 extends into the condenser 20 and the connection to the cleaning tank 24 is provided via a connecting line 22. The cleaning tank 24 is connected to an outlet 30 via a wastewater pump 32 and to a return line 40 via a circulating pump 42.

During a cleaning method, washing liquor 26, which can be introduced into the cleaning tank 24 with a determined water level 27, is conveyed from the cleaning tank 24 into the cooking chamber 10 by means of the circulating pump 42 in order to carry out cleaning. The washing liquor flows out of the cooking chamber 10, passing through the strainer 14 and back into the cleaning tank 24. The washing liquor 26 is thus circulated.

During a cooking method, instead of the washing liquor 26 shown in FIG. 5, a pump sump is located upstream of the outlet to the pumps 32, 42. Juices which arise during boiling, roasting, grilling or the like here flow out from the cooking chamber 10 via the strainer 14 into the pump sump.

A turbidity sensor 28 is arranged in the cleaning tank 24. The position of the turbidity sensor 28 is selected such that, during a cleaning method, the washing liquor 26 flows effectively around it and, that during a cooking method, a location below the water level 27 of the pump sump is ensured. The turbidity sensor 28 need not necessarily be fastened for this purpose to the bottom of the cleaning tank 24 but can also be provided in a wall. The position in the bottom shown in FIG. 5 is particularly favorable for the construction geometries shown.

The water level 27 can be controlled by means of the wastewater pump 32, or alternatively via an outlet valve (e.g. ball valve), a defined drain orifice or the like.

In the cooking appliance 1 of FIG. 5, it is possible to determine a degree of soiling in particular of the cooking chamber 10 via the turbidity sensor 28 not only during a cleaning operation, but also during a cooking operation. It is essential to this end for the turbidity sensor 28 to be located in a water reserve, either in the form of a washing liquor or a pump sump, downstream of the cooking chamber 10, which generally means below the cooking chamber 10, as is also indicated in FIG. 5.

If turbidity values are detected for example during a cooking method, it is possible to draw a conclusion therefrom about the soiling of the cooking chamber 10 which is dependent on the quantity and nature of the foodstuff being cooked. On the basis of the determined degree of soiling, it is then in turn possible to determine a suitable cleaning method which is to proceed later. This cleaning method can be output as a suggested cleaning program, either on a display means on the cooking appliance 1 or on a central control console of a kitchen network into which the cooking appliance can be integrated. The display may for example appear after completion of the cooking operation automatically or only on request.

In a further embodiment, after introduction of the washing liquor into the cooking chamber of a cooking appliance, in which foodstuffs can in particular be exposed to hot air, steam and/or microwaves, a cleaning operation is started either automatically after determination of a parameter T₀ at a point in time t₀ or by selection of a cleaning program by a user. Automatic determination or manual selection of the cleaning program also results in the selection of cleaning parameters, such as for example a predetermined temperature and a cleaning product chemistry to be used. If the cleaning program comprises a plurality of cleaning phases, the cleaning parameters are provisionally selected for all cleaning phases.

FIG. 6 shows by way of example a possible parameter progression over time, from which the cleaning progress can be inferred. At the beginning of cleaning, the turbidity in the washing liquor may for example increase sharply. Thereafter, turbidity does not increase any further, but instead declines. This is for example because, without being limited thereto, a very large number of particles which are detached from the cooking chamber wall are present in the washing liquor at the beginning of cleaning. These numerous particles cause severe diffraction of the light. These first values for turbidity provide direct information about how severely the cooking appliance interior is soiled. In the case of slight soiling, the decline in the curve is correspondingly low, while the decline is greater in the case of severe soiling and thus severe turbidity of the washing liquor. Turbidity falls during cleaning, as the appliance becomes cleaner, since more soil particles dissolve in the washing liquor than new ones are detached in the cooking chamber. The turbidity curve rises as a consequence. The proportion of particles in the washing liquor and thus the degree of turbidity can be inferred for example from FIG. 7, wherein it is apparent that the particles become ever smaller over the course of time and ultimately completely dissolve, and thus turbidity declines or, ideally, disappears.

Relatively shortly after the start for example of a first cleaning phase, a first turbidity value TS₁ is determined at a first point in time t₁ by means of one or more sensor(s) present in the cooking chamber. Then, at a predetermined second point in time t₂, the current turbidity of the washing liquor is determined, thus a second turbidity value TS₂ is determined. On the basis of the two turbidity values, a first difference is then determined: ΔTS₁=TS₂−TS₁. The difference value determined in this manner is then compared with a predetermined first limit value. If, for example, the first limit value is exceeded, i.e. ΔTS₁>TS_(limit), a second cleaning phase is started. After an identical time interval has elapsed, a third turbidity parameter TS₃ is detected and a second difference, i.e. ΔTS₂=TS₃−TS₂, determined and compared with the first or a second limit value. Should the limit value again be exceeded, i.e. ΔTS₂>TS_(limit), a third cleaning phase begins automatically. In the example in FIG. 6, this procedure is repeated another three times. The cleaning phase which starts over each time can be carried out unchanged or with changed cleaning parameters, such as for example a changed temperature. When the difference finally undercuts the limit value, i.e. ΔTS<TS_(limit), the cleaning operation is terminated since the appliance has achieved the desired cleanliness. It is likewise possible to use the measured values obtained to generate a measurement curve, for example by a regression analysis, as shown in FIG. 6. On the basis of the curvature and/or gradient of the curve, it is possible to establish when the cooking appliance is clean and/or which cleaning parameters should be used in subsequent cleaning phases.

Selection of the cleaning program is non-critical in a method because the cleaning phases of the particular cleaning operation which has been started are automatically adapted. This enables the provision of a cooking appliance with only one cleaning program, which is preferably an environmentally friendly “eco” program which for example requires additional cleaning agent and/or elevated temperatures only in the case of a respective degree of soiling. In one embodiment, the cooking appliance itself determines the cleaning program, i.e. the cleaning parameters, by ascertaining the initial turbidity value.

In addition, the cooking appliance may also be self-learning, since it can store changed cleaning parameters for future cleaning operations. A linkage to cooking programs can also be made by correlating the detected degree of soiling with the cooking program(s) which has/have previously been run.

FIG. 7 shows a portion of one possible procedure of the cleaning method. At the beginning, a first turbidity value (TS₁) is determined and evaluated. The cleaning phase is started, and in particular determined by evaluation of the turbidity value TS₁. At the end of the cleaning phase (in this case: after 8 min), a second turbidity value TS₂ is determined. By calculating the difference and comparing the value obtained with a limit value, it is possible to determine whether a desired degree of cleaning has or has not been achieved. Should the desired degree of cleaning not have been reached, the value TS₂ is stored as a new value TS₁ and the cleaning phase starts over again.

FIG. 8 shows the complete cleaning method, in which introductory steps prior to the method steps described in relation to FIG. 7 are described for carrying out a component test, steaming the cooking chamber, a brief circulation phase (in this case 60 seconds) and a pause of the circulating pump. As is additionally indicated in FIG. 8, the cleaning method is terminated when the limit value is reached by rinsing the appliance , for example in a rinsing phase.

FIG. 9 finally shows two typical curve progressions for moderate soiling and light soiling, in each case by cleaning without using chemicals, i.e. without a cleaning agent. The characteristic progression of the cleaning curve reveals that no cleaning agent has been used. The initial values are not reached again at the end of cleaning because soiling still remains in the cooking appliance. The characteristic peak for the rinsing phase (see FIG. 3) is only very small, see arrow in FIG. 9.

The features of the invention disclosed in the above description, in the claims and in the drawings may be of significance for implementation of the invention in its various embodiments either individually or in any desired combination.

LIST OF REFERENCE NUMERALS

1 Cooking appliance

10 Cooking chamber

12 Drain

14 Strainer

16 Fan wheel

20 Condenser

22 Connecting line

24 Cleaning tank

26 Washing liquor

27 Water level

28 Turbidity sensor

30 Outlet

32 Wastewater pump

40 Return line

42 Circulating pump 

1. A method for identifying a degree of soiling of an interior of a cooking appliance during at least one of a cleaning operation and a cooking operation, comprising determining at least one parameter of a liquid over time and determining the degree of soiling of the interior from a change in the at least one parameter, wherein the at least one parameter is a physical variable which is determined via at least one sensor.
 2. The method according to claim 1, wherein at least one first parameter of the at least one parameter is determined at a first point in time of the cleaning or cooking operation and at least one second parameter of the at least one parameter is determined at a second point in time of the cleaning or cooking operation, and the degree of soiling is determined from at least one of a change in and difference between the at least one first parameter and the at least one second parameter, and comparing at least one of a change in and difference between the at least one first parameter and the at least one second parameter with at least one predetermined or predeterminable limit value.
 3. The method according to claim 1, wherein, in order to determine the degree of soiling at least one of: the at least one parameter is detected at a plurality of points in time, the progression of at least one parameter is detected over time, at least one of at least one maximum and at least one minimum of the progression of the at least one parameter is detected over time, at least on of the gradient and curvature of the progression of the at least one parameter is detected over time, and a regression analysis of the parameters is carried out.
 4. The method according to claim 1, wherein at least one of the at least one sensor is installed in at least one of the cleaning path of the liquid and downstream of the cooking chamber, and an open- or closed-loop control device carries out at least one of the measurement and/or the evaluation of measured values obtained, wherein the open- or closed-loop control device preferably comprises the at least one sensor.
 5. The method according to claim 1, wherein the time interval between two successive measurements is lengthened or shortened via the open- or closed-loop control device, as a function of at least one of the detected parameters, the detected progression of the parameters, the detected maximum of the progression of the parameters, the detected minimum of the progression of the parameters, at least one of the detected gradient and curvature of the progression of the parameters, and the regression analysis.
 6. The method according to claim 1, wherein at least one of the degree of soiling and at least one, in particular previously carried out program, selected from a plurality of cleaning programs and/or cooking programs, is determined, in particular via the open- or closed-loop control device, as a function of at least one of the detected parameters, the detected progression of the parameters, the detected maximum of the progression of the parameters, the detected minimum of the progression of the parameters, at least one of the detected gradient and curvature of the progression of the parameters and the regression analysis.
 7. The method according to claim 1, wherein the identified or determined degree of soiling is displayed at least temporarily, automatically or on request.
 8. The method according to claim 1, wherein at least one of the at least one parameter is selected from at least one of turbidity, pH, conductivity, viscosity, color, refractive index, fluorescence, adsorption, emission and density of the washing liquor, and the at least one sensor is selected from at least one of an optical sensor, a turbidity sensor, a pH sensor, a conductivity sensor, a viscosity sensor, a color sensor, a sensor for measuring refractive index, a fluorescence sensor, a sensor for measuring adsorption and/or emission and a density sensor.
 9. The method according to claim 6, wherein the minimum of the time progression of parameters for turbidity is detected or determined and, on the basis of the parameter at the minimum, the degree of soiling is determined, wherein the parameter at the minimum is smaller at a greater degree of soiling.
 10. The method according to claim 1, wherein as a function of the identified or determined degree of soiling, at least one of an ongoing cleaning operation is adapted, at least one of a suggestion for and a modification to a future cleaning program is determined, at least one characteristic variable of at least one of a previous and the current cooking operation is determined, and a user behavior is determined.
 11. The method according to claim 1, wherein the liquid selected is a washing liquor during a cleaning operation or a water reserve upstream from an outlet of the cooking appliance during a cooking operation.
 12. The method according to claim 1, wherein at least one of the parameters of the cleaning operation is paused during a cleaning operation prior to determination.
 13. The method according to claim 12, wherein the duration of the pause in at least one of the cleaning operation and the timing of the pause in the cleaning operation is determined, in particular via the open- or closed-loop control device, as a function of at least one of the detected parameters, the detected progression of the parameters, the detected maximum of the progression of the parameters, the detected minimum of the progression of the parameters, at least one of the detected gradient and curvature of the progression of the parameters, and the regression analysis.
 14. A cooking appliance for cooking food items in a cooking chamber; comprising at least one sensor; and an open- or closed-loop control device for carrying out a method according to claim
 1. 15. The cooking appliance according to claim 14, wherein the cooking appliance is self-learning.
 16. The cooking appliance according to claim 14, further comprising an output device, comprising a display means, for the detected degree of soiling.
 17. The cooking appliance according to claim 14, wherein the sensor is arranged downstream of the cooking chamber with the liquid flowing therearound.
 18. The cooking appliance according to claim 14, wherein the cooking chamber is connected, with interposition of a strainer, to at least one of a condenser and a cleaning tank, and the sensor is arranged in at least one of the condenser and/or cleaning tank.
 19. The cooking appliance according to claim 14, wherein at least one of the condenser and cleaning tank is connected to at least one of an at least temporarily closable outlet and to an at least temporarily closable return line to the cooking chamber.
 20. The cooking appliance according to claim 19, wherein at least one of the outlet is temporarily closable via a pump or a valve, and the return line is connected to at least one of a pump and a valve.
 21. The cooking appliance according to claim 20, wherein the sensor is arranged in the water reserve provided by at least one of a sump of the pump of the outlet and of the pump of the return line.
 22. The cooking appliance according to claim 17, wherein the sensor is arranged in the water reserve between the cooking chamber and the outlet from the cooking appliance.
 23. The cooking appliance according to claim 17, wherein the water level of the water reserve is adjustable via at least one of an open- or closed-loop control device in operative connection with the pump of the outlet, the pump, the return line, and a shut-off device.
 24. A method for cleaning a cooking appliance interior, comprising the following steps after a start of a cleaning operation having at least one cleaning phase: introducing a washing liquor into the cooking appliance interior and starting the at least one cleaning phase using one or more cleaning parameters; determining at least one first parameter TS₁ of the washing liquor at a first point in time t₁ of the cleaning operation and determining at least one second parameter TS₂ of the washing liquor at a second point in time t₂ of the cleaning operation; and determining a degree of cleaning of the cooking appliance interior from a change in the parameters; wherein, depending on the change in the parameters, at least one of the steps are repeated and at least one of the cleaning parameters is adapted or the at least one cleaning phase is terminated.
 25. The method according to claim 24, wherein, for determining the degree of cleaning of the cooking appliance interior at a plurality of points in time, at least one of the at least one parameter is detected, the progression of the parameters over time is detected, at least one of at least one maximum and at least one minimum of the progression of the parameters over time is detected, at least one of the gradient and curvature of the progression of the parameters is detected over time, and a regression analysis of the parameters is carried out.
 26. The method according to claim 24, wherein the degree of cleaning of the cooking appliance interior is determined from the change in and/or difference between the first parameter relative to the second parameter, ΔTS₁=TS₂−TS₁, and by comparing the change in and/or difference between the parameters with at least one known limit value TS_(limit).
 27. The method according to claim 24, wherein at least one of in that initial cleaning parameters are determined by determining at least one parameter TS₀ at a point in time t₀, and in that initial cleaning parameters are determined by manual selection of a cleaning program.
 28. The method according to claim 24, wherein the at least one parameter is a physical variable which is at least one of determined via at least one sensor and selected from at least one of the turbidity, pH, electrical conductivity, viscosity, color, refractive index, fluorescence, adsorption, emission and density of the washing liquor.
 29. The method according to claim 28, wherein at least one of the at least one sensor is installed in at least one of the cleaning path of the washing liquor, the control box, the pump sump, the cooking chamber, the cleaning product box and a pipe of the cooking appliance, an open- or closed-loop control device carries out at least one of the measurement and the evaluation of the measured values obtained, wherein the open- or closed-loop control device preferably comprises the at least one sensor, and in that the at least one sensor is selected as an optical sensor, a turbidity sensor, a pH sensor, a conductivity sensor, a viscosity sensor, a color sensor, a sensor for measuring refractive index, a fluorescence sensor, a sensor for measuring adsorption and emission, and a density sensor.
 30. The method according to claim 24, wherein the first point in time t₁ is selected during the at least one cleaning phase and the second point in time t₂ after the at least one cleaning phase, wherein the cleaning operation is preferably terminated when the at least one limit value is reached.
 31. The method according to claim 24, wherein at least one of as a function of the identified or determined degree of cleaning, at least one of at least one cleaning parameter, at least one limit value, and at least one time interval between the determination of two parameters is at least one of determined, stored and displayed for at least one of at least one subsequent cleaning phase of the cleaning operation and a future cleaning operation, in that, as a function of the identified or determined degree of cleaning, at least one cleaning parameter of at least one previous cleaning phase of the cleaning operation is at least one of determined, stored and displayed, in that, as a function of the identified or determined degree of cleaning, at least one characteristic variable of at least one previous cooking operation is at least one of determined, stored and displayed, and as a function of the identified or determined degree of cleaning, a user behavior is at least one of determined, stored and displayed.
 32. The method according to claim 24, wherein the at least one or plurality of cleaning parameters are selected from at least one of the duration of the at least one cleaning phase, the temperature during the at least one cleaning phase, the speed of circulation of the cleaning agent, the acceleration of circulation of the cleaning agent, the chemistry of the cleaning agent, the quantity of cleaning agent, the quantity of washing medium, in particular water, and a combination thereof.
 33. The method according to claim 24, wherein at least one of the at least one cleaning phase is selected from at least one of a cleaning product phase, a rinse aid phase and a descaler phase, and the chemistry of the cleaning agent is selected from at least one of a cleaning product, a rinse aid and a descaler.
 34. A cooking appliance for cooking food items comprising a cleaning device, at least one sensor and an open- or closed-loop control device for carrying out a method according to claim
 24. 35. The cooking appliance according to claim 34, wherein at least one of the cooking appliance comprises at least one dispenser for the cleaning agent, the cooking appliance further comprises the washing medium, and the cooking appliance is self-learning. 